1. Field of the Invention
This invention relates to electrical testing devices and more particularly to a bar-to-bar armature tester for determining the presence of shorted coils, open circuits, or reverse windings.
2. Description of the Prior Art
Various attempts have been made in the prior art to provide an adequate tester for testing coil windings of an armature. The prior art devices however have been unreliable, expensive and/or complicated.
One such device is disclosed in U.S. Pat. No. 1,494,232 to Friedly. This device is a relatively large and complicated unit designed for testing not only armature coil windings but also for testing various other electrical equipment. The Friedly device requires the user to connect the probe ends into the proper terminals and to place the probes by hand onto the proper commutators. Furthermore, Friedly's testing device is adapted to detect short circuits and open circuits of the coils but does not provide for an indication that a coil has become reversed by cross winding or the like. Also, Friedly has no provision for adjusting the voltmeter; and therefore, cannot properly indicate the status of the coil for all sizes of armature since there would be no way to adjust the reference voltage.
Another prior art armature testing device is disclosed in U.S. Pat. No. 2,463,567 to Samstag. Samstag has overcome one problem of portability but includes many other disadvantages, such as the fact that all of the circuitry of the testing device is exposed and can be readily shorted-out by contacting the armature to be tested. Furthermore, the Samstag device provides no protection against damage due to dropping of the device, nor against damage caused by collection of dirt in the instrumentation of the device. The probes which contact the device to be tested are connected onto the testing device by way of wing nuts which along with the circuitry leading up to the probes are exposed and may come in contact with armature coil windings and cause improper readings. Samstag utilizes a millimeter, a rheostat and a single battery in circuit. The circuitry contemplated by Samstag is such that energy from the battery is lost in the rheostat prior to sending the current to the armature; thereby, causing unnecessary power loss and shortening of the life of the battery. Furthermore, Stamstag's device is contemplated as being used on armatures before being taken out of the motor and not for use in repairing or rewinding an armature in a repair shop.